Dynamic Range Processing: compressors, limiters, expanders, band compression, distortion

In this article, I will explain what is Dynamic Range Processing. Dynamic Range is one of the important part of audio theory and umfamiliar thing for who doesn’t know audio theory well. So I will show and explain you more specifically about compressors, limiters, expanders, band compression, distortion. Also, I will post some videos and pictures that show this element is how to operate and why we use this tool.

Dynamic Range

The dynamic ranges is the difference between this softest and the loudest signal a device can handle. And it’s also the difference between the loudest and the softest level of an audio signal. The dynamic range of digital audio 16bits is 96 decibel. The average dynamic range of magnetic tape is around 60 up to 70 dB. If we’re going to look at radio. An AM-signal has around 40dB of dynamic range. A fm-signal has around 70dB of dynamic range.

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Dynamic Range

Let’s talk about the dynamic range of music. Classical music is known for it’s big dynamic range. Because the difference between the soft-parts and loud-parts is big. If we’re going to look at more modern type of music. We see that we heavily compress this music. -therefore it has a small dynamic range

What is a compressor?

An audio-compressor is being used on recordings to control the dynamic- content of that channel. The basic function of a compressor is that when the level, or signal, gets too loud, the compressor will automatically reduce the volume. In other words, audio compression is a method of reducing the dynamic range of a signal.

Compressors are generally used as an insert-effect during mixing. That means it will be inserted into one channel and affect the dynamic content of that channel that it’s being inserted on. Because you want to dynamically control the kickdrum differently than you want to control the vocal. Compressors can also be used on whole mixes, where they’re being used for mastering purposes.

* Band compresssion

Multi-band compression is one of the most powerful processing techniques available to the recording engineer. In essence, a multi-band compressor comprises a set of filters (similar to a PA system’s active crossover) that splits the audio signal into two or more frequency bands. Three- or four-band compressors are perhaps the best compromise between versatility and ease of setting up. After passing through the filters, each frequency band is fed into its own compressor, after which the signals are recombined. The main advantage of multi-band compression is that a loud event in one frequency band won’t trigger gain reduction in the other bands, so when that loud kick drum comes along, instead of pulling the whole mix down with it, only the low-frequency sounds (kick and bass instrument) will be compressed, leaving the mid-range and high frequencies untroubled. Similarly, a loud event in the mid-range won’t affect the extreme high or low frequencies for the same reason. This is a video using Multi-band compression

What is a limiter?

Limiting is a type of dynamic range compression. A limiter is a kind of compressor designed for a specific purpose — to limit the level of a signal to a certain threshold. Whereas a compressor will begin smoothly reducing the gain above the threshold, a limiter will almost completely prevent any additional gain above the threshold. A limiter is like a compressor set to a very high compression ratio (at least 10:1, more commonly 20:1 or more).

What is an expander?

Audio expansion means to expand the dynamic range of a signal. It is basically the opposite of audio compression. It makes the dynamic range of the signal larger by making soft sounds even softer and therefore increasing the dynamic range. Like compressors and limiters, an audio expander has an adjustable threshold and ratio. Whereas compression and limiting take effect whenever the signal goes above the threshold, expansion effects signal levels below the threshold. an expander works with a ratio. This is a video which explain how expanders do works with a ratio.

What is distortion?

The speaker send the sound with air. So It could be more distorted than other audio tools. So when the sound is distorted, the graph will change like this picture. Many companies divise a lot ways In order to minimize this distortion.

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In conclusion, There are some technic processes among dynamic range. These processes make the audio more active, lively. In order to make good sounds matching a video well, we’d better using this technics and knowing how to operate some tools naturally. The theory of this part is so hard to understand for the first time. However, when we get used to use this skill, we can grow our editing audio ability.


Audio-Aron – This is my presentation document

Webgraphy

http://en.wikipedia.org/w/index.php?title=Special:Search&limit=20&offset=20&profile=default&search=band+compression

http://www.soundonsound.com/sos/aug02/articles/multiband.asp

http://blog.naver.com/dejc2000/10046994523 ( Korea web site )

http://en.wikipedia.org/wiki/Limiting

http://cafe.naver.com/easternsound/278 ( Korea web site )

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